HMI41 AND HMP42
Operating Manual
M210317EN-A
12
5.2
Calibration with trimmer potentiometers
5.2.1
Humidity calibration
The HMI41 indicator and HMP42 probes are fully calibrated at the factory so
there should be no immediate need for re-calibration. The recommended
calibration interval is one year. However, calibration should be performed
always when there is a reason to believe that the adjustments have changed.
Humidity calibration of the HMP42 probe is done by adjusting trimmer
potentiometers. The potentiometers are located under a protective plug. The
potentiometer marked T (temperature) is for factory use only; DO NOT make
any adjustments. To make sure that this potentiometer is not accidentally
touched when adjusting the other two, turn the plastic plug aside without
removing it completely (see Figure 5.2.1).
For adjusting the potentiometers, use a trimming wrench provided with the
probe, or some other suitable tool, e.g. a ceramic 1.5 mm slot screwdriver.
wet
T
W
D
D
W
dry
Figure 5.2.1
Adjusting the trimmer potentiometers
A two point calibration is performed with the HMK15. Calibrator or the probe
can be sent to Vaisala. The probes must always be re-calibrated if the sensor
head set is changed.